There are so-called two-piece automobile wheels in which a generally cylindrical wheel rim and a generally disc-like wheel disc are welded to each other. As such two-piece automobile wheels, there are known full-face automobile wheels in which a front flange portion is formed at an outer peripheral edge portion of the wheel disc.
An example of the full-face automobile wheels is proposed in Japanese Unexamined Patent Publication No. JP-A-Hei 11-42901, for example. As shown in FIG. 16, a wheel rim “f” includes a front bead seat portion “g” provided at one opening edge portion and a back flange portion “j” provided at the other opening edge portion. A wheel disc “p” includes a front flange portion “r” provided at an outer peripheral edge portion and folded backward in a curved shape. An opening end portion “h” of the front bead seat portion “g” of the wheel rim “f” and an inner peripheral end portion “v” of the front flange portion “r” of the wheel disc “p” are welded to each other over the entire circumference of the wheel to form a full-face automobile wheel “m”. The thus configured full-face automobile wheel “m” can secure a large design surface on the wheel disc “p”, advantageously providing high design quality.
In the configuration disclosed in Japanese Unexamined Patent Publication No. JP-A-Hei 11-42901, the opening end portion “h” of the front bead seat portion “g” of the wheel rim “f” and the inner peripheral end portion “v” of the front flange portion “r” of the wheel disc “p” are welded to each other so that a welded portion “i” joins the wheel rim “f” and the wheel disc “p” to each other. When an automobile equipped with the automobile wheel “m” is running, a load acts on the wheel rim “f” via a tire, and a load acts on the wheel disc “p” via an axle. The front flange portion “r” of the automobile wheel “m” includes an annular front peripheral portion “s” provided on the design surface side, and an annular back peripheral portion “t” formed continuously from the annular front peripheral portion “s” and folded backward in a curved shape. A hollow area is formed between the annular front peripheral portion and the annular back peripheral portion “t” Due to the shape of the front flange portion “r” described above, the front flange portion “r” tends to be repeatedly elastically deformed by the load acting on the wheel rim “f” and the load acting on the wheel disc “p”, and tends to be subjected to a stress concentration. Further, because the front flange portion “r” is folded backward through a pressing process or the like, a residual stress may be caused at a curved outer peripheral edge portion of the front flange portion “r”. The durability of the front flange portion “r” is limited by the residual stress and the stress concentration due to the loads described above.
The welded portion “i” described above at which the opening end portion “h” of the front bead seat portion “g” and the inner peripheral end portion “v” of the front flange portion “r” are welded to each other also tends to be subjected to a stress concentration caused by the above loads acting while the vehicle is running. If the welded portion “i” should be cracked (broken), air in the tire may leak. Thus, it is desired to improve the durability of the welded portion “i”.
The present invention proposes an automobile wheel that includes a wheel disc with a front flange portion folded backward and a wheel disc and that can exhibit high durability.